The only good covered storage I know of in the Anchorage area is McGhan Storage Services out at Big Lake, Alaska which is about 50 miles north of Anchorage. I've used them before.
They have up to 50' long covered stall. If I remember correctly the roof is rated for 80# per sq ft.
In the large covered storage area, they don't plow it during the winter, when you've parked your rig and it snows, it's then there for the winter. While the area is fenced and gated, the lack of snow plowing is also a good safety feature because thieves are lazy.
McGhan Storage ServicesI would call them soon, they may not have any spaces left for the winter.
As I side note, I store my TT in my back yard in Anchorage as the snow hasn't been deep enough to worry about the last couple of years. Three feet of snow isn't going to hurt it.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.